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<td class="header">&nbsp; Azimuth Shift Estimation using Enhanced Spectral Diversity (EDS)<br>
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<h3>Sentinel-1 Azimuth Shift Estimation using ESD</h3>
<p class="MsoNormal" style="margin: 6pt; font-family: Verdana,Arial,Helvetica,sans-serif; color: rgb(0, 0, 0); font-size: 12px; font-style: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px;"><span>This operator follows the</span><span style="color: rgb(0, 0, 0); font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 12px; font-style: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; background-color: rgb(255, 255, 255); display: inline ! important; float: none;"> S-1 Back Geocoding operator in the TOPS InSAR processing chain</span><span>.&nbsp;The
operator&nbsp;estimates a constant azimuth offset for the whole
sub-swath using a Enhanced Spectral Diversity (ESD) method. The ESD
approach exploits the data at the overlapped area of the adjacent
bursts. The estimation is done for a number of windows in every
overlapped area and the final azimuth offset is obtained by averaging
all the estimations.<span>&nbsp;</span><br></span></p><p class="MsoNormal"><span>The
estimated&nbsp;azimuth shifts (overall shift for the whole sub-swath
and shifts estimated for all windows in the overlapped areas) are saved
in both the metadata of the output product and&nbsp;in an ASCII file
with reference acquisition date and "_azimuth_shift" in the file name. The
file can be found at user's \.snap\var\log folder.<span>&nbsp;</span></span></p><p class="MsoNormal"><span><span></span></span>User
can review the azimuth shifts estimated for all sub-swathes and decide
which shift value will be used in the azimuth shift correction. To
perform the azimuth correction, user can run the S-1 Enhanced Spectral
Diversity operator with the user selected azimuth shift value.&nbsp;</p><p class="MsoNormal">Generally
users do not need to run this operator if they do not need to review
the azimuth shift values. They can run the S-1 Enhanced Spectral
Diversity operator directly where the azimuth shift is estimated using
EDS and used directly in the azimuth shift correction. However, there
are some cases where data in one sub-swath is corrupted and cannot be
used in the azimuth shift estimation. In this case, users can use the
azimuth shift estimated for other sub-swath in the correction of
current sub-swath.
 <span style=""></span></p>
 
<h4>Input <br>
</h4>



<ul>
<li><span style="color: rgb(0, 0, 0); font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 12px; font-style: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; background-color: rgb(255, 255, 255); display: inline ! important; float: none;">The
input to this operator is the resulting product from the S-1 Back
Geocoding operator. It is the co-registered reference and secondary images for
the same sub-swath and same polarization (e.g. IW1 - VV)</span>.
  </li>
</ul>

<h4>Output <br>
</h4>




<ul>
<li>The output product of the operator is the same as the input product
except that the metadata has been updated with the estimated azimuth
shifts. </li>
</ul>


<h4>Parameters Used<br>
</h4>




<ul>
<li style="margin-top: 4pt; margin-bottom: 4pt;">Coherence Threshold for Outlier Removal:<span> Pixels with coherence higher than the threshold are used in azimuth shift estimation. </span><br></li><li style="margin-top: 4pt; margin-bottom: 4pt;">Number of Windows Per Overlap for ESD: The number of windows for azimuth shift estimation for each overlap area.</li></ul><img style="width: 434px; height: 440px;" alt="" src="images/AzimuthShiftEstimationUsingESDOp.jpg"><ul>
</ul>
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